This year, in collaboration with Dorothy Erie at the University of North Carolina at Chapel Hill, I published a review article describing recent studies of DNA mismatch repair and its relationship to DNA replication enzymology, including fidelity. We also continued to study the role of mismatch repair in regulating the genome-wide mutation rates of yeast cells harboring variant, proofreading-deficient alleles of the major leading and lagging strand enzymes, DNA polymerases epsilon and delta. These studies, which are being performed in mismatch repair-proficient and MMR deficient yeast cells, are well underway. They should be informative regarding the roles of nucleotide selectivity, proofreading and mismatch repair to genome wide mutation rates for base substitution and insertion-deletion errors.